<html>
  <head>
    <title>Main</title>
    <style>
      area {
        border: 2px ridge;
      }

      box {
        background-color: rgba(106, 24, 238, 0.26);
        height: 5em;
        margin: 1em;
        width: 5em;
      }
    </style>
  </head>

  <body>
    <div class="area">
      <div class="box rAF"></div>
    </div>
    <br />
    <script>
      function setNewArea() {
        let el = document.createElement('div');
        el.setAttribute('class', 'area');
        el.innerHTML = '<div class="box rAF">1111</div>';
        document.body.append(el);
      }
      setNewArea();
    </script>
  </body>
</html>
